Digital watermarking technology (also known as steganography) encompasses a great variety of techniques by which one or more bits of digital data are hidden in some other object, without leaving human-perceptible evidence of alteration or data representation.
Digital watermarks can take many different forms, and serve many different applications (e.g., authenticating objects; conveying or linking to object metadata; specifying rules for use; triggering device actions or content delivery; conveying decryption instructions, logically binding content to users or devices, etc.). Patents illustrating same include U.S. Pat. Nos. 6,614,914, 6,823,075, 6,804,376, 6,788,800, 6,771,797, 6,768,809, 6,768,808, and 6,750,985.
The most familiar forms of steganography are those in which information is concealed in objects such as sound and image files. For example, the least significant bits of pixels defining a graphic can be altered to convey plural bits of hidden information. The graphic appears essentially pristine to a human viewer, but a suitably-programmed processor can decode the plural-bit payload from the graphic data. Similarly, a graphic may be stored in higher resolution than it can be displayed, and the display functions may disregard the superfluous information—allowing these extra thousands of bits to be used for other purposes. Many more sophisticated techniques for hiding information are detailed in the watermarking patent literature, such as the patents referenced above. However, objects that can conceal hidden data include more than just audio and imagery files. There is a growing field of art in concealing data within software instructions, e.g., in the pattern or order of instructions, in the pattern of registry usage, etc. Some such techniques are detailed, for example, in U.S. Pat. Nos. 6,834,343 and 6,829,710.
BIOS technology is also well known, and traditionally has served two primary purposes. The first is to initialize and test a computer's hardware and to collect hardware configuration information (the Power On Self Test process—POST). The second is to provide the collected hardware information to a loader that initiates the operating system (OS). Exemplary patent publications in the field include U.S. Pat. Nos. 6,557,104 6,791,572 6,772,313 6,734,864 6,633,976 6,622,179 6,598,165 and 6,564,318.